In situ low-relief landscape formation as a result of river network disruption
In situ low-relief landscape formation as a result of river network disruption
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DOI：
10.1038/nature14354
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发表时间：
2015-04
期刊：
影响因子：
64.8
通讯作者：
Rong Yang;S. Willett;L. Goren
中科院分区：
文献类型：
--
作者：
Rong Yang;S. Willett;L. Goren
地球上的景观保留了它们形成时的构造、环境和气候历史的记录。景观趋于平衡，河流达到稳定的坡度，平衡了海拔的构造生产，山坡达到足够陡的坡度，将物质输送到河道。平衡低起伏表面通常出现在低海拔地区，坡度与海平面一致。然而，有许多高海拔，低起伏表面的例子，通常被称为残遗景观，或作为高架平原。这些不分级到海平面，通常被解释为隆起的旧景观，保留以前，更温和的构造条件。在这里，我们测试这个模型的景观演化，通过数字地形分析的一组据称残留景观的东南边缘的青藏高原，一个地理上最复杂的，气候变化和生物多样性的地区。我们发现，与理论相反，所谓的表面是不符合逐步建立一个新的，陡峭的河流等级，因此，他们不一定可以被解释为一个旧的，低浮雕表面的残余。我们提出了一个替代模型，数值实验的支持下，构造变形破坏了区域河流网络，它的残余孤立和饥饿的流域，从而无法平衡构造隆起。这意味着低地形和低侵蚀率的状态是原地发展的，而不是保持过去的侵蚀条件。
Landscapes on Earth retain a record of the tectonic, environmental and climatic history under which they formed. Landscapes tend towards an equilibrium in which rivers attain a stable grade that balances the tectonic production of elevation and with hillslopes that attain a gradient steep enough to transport material to river channels. Equilibrium low-relief surfaces are typically found at low elevations, graded to sea level. However, there are many examples of high-elevation, low-relief surfaces, often referred to as relict landscapes,, or as elevated peneplains. These do not grade to sea level and are typically interpreted as uplifted old landscapes, preserving former, more moderate tectonic conditions. Here we test this model of landscape evolution through digital topographic analysis of a set of purportedly relict landscapes on the southeastern margin of the Tibetan Plateau, one of the most geographically complex, climatically varied and biologically diverse regions of the world. We find that, in contrast to theory, the purported surfaces are not consistent with progressive establishment of a new, steeper, river grade, and therefore they cannot necessarily be interpreted as a remnant of an old, low relief surface. We propose an alternative model, supported by numerical experiments, in which tectonic deformation has disrupted the regional river network, leaving remnants of it isolated and starved of drainage area and thus unable to balance tectonic uplift. The implication is that the state of low relief with low erosion rate is developingin situ, rather than preserving past erosional conditions.